The Causes of Congestive Heart Failure

Click the icon to see an image of dilated cardiomyopathy.

Hypertrophic Cardiomyopathy. In hypertrophic cardiomyopathy, the heart muscles become thick and contract with difficulty. Some research indicates that this occurs because of a genetic defect that causes a loss of power in heart muscle cells and, subsequently, lower pumping strength. To compensate for this power loss, the heart muscle cells grow. This condition, rare in the general population, is often the cause of sudden death in young athletes.

Click the icon to see an image of hypertrophic cardiomyopathy.

Corrective Mechanisms, Remodeling, and the Failing Heart

High blood pressure, heart attacks, or other initial processes that impair the pumping actions of the heart trigger a number of hormonal and neurochemical mechanisms to correct imbalances in pressure and blood flow. Unfortunately, while these corrective responses help in the short term, they increase the work of the heart. The mechanisms are now viewed as major contributors to the end stages of heart failure. Some are described briefly in the following sections.

Remodeling. The heart responds to high blood pressure and overload by enlarging in order to increase blood input. This leads to structural damage called remodeling:

• In order to accommodate the increased blood input, the heart muscle cells elongate. The muscular walls of the heart that they form become thinner and inefficient.
• The muscle cells undergo other changes that result in calcium loss. Calcium is a mineral that is crucial for healthy heart contractions.
• The thinner heart muscles and the impaired heart contractions further weaken the heart's pump.
• Mitral valve regurgitation is a possible outcome of remodeling. The mitral valve regulates blood flow between the two chambers on the left side of the heart. In response to remodeling, the structural changes in the heart may distort the mitral valve so that the blood leaks backward into the left atrium of the heart instead of flowing out into the body's circulation.
• These changes are generally irreversible, although heart pacemakers and certain drugs, including beta-blockers and ACE inhibitors, may reverse some of the remodeling in some patients.